1. Field of the Invention
The invention concerns a mechanical linking means between a first member and a second member such as a control member and a controlled part.
2. Description of the Related Art
A gas turbine engine includes, for instance, doors blanking off the discharge apertures of the low pressure compressor in order to control the operation thereof. The doors are provided on the external wall of the tunnel downstream of the compressor, and distributed regularly around the axis of the engine. There may be ten, for example. They are mounted generally in order each to tip around an axis situated in a plane transversal to the axis of the engine. Simultaneous opening of the doors is actuated by means of an annular control member, brought into rotation by an appropriate jack. The rotational movement of this ring is transformed into an axial movement by square-shaped transmission parts. A branch thereof is connected to a yoke integral with the door that it controls by dint of a link.
Taking the assembly and manufacture tolerances of the parts into account, a means for adjusting the length of the link actuating each door is required. This means enables to ensure that all the doors occupy the same reference position. Notably, when the control ring is placed in the closing position of the doors, the latter should all be able to blank off the apertures correctly.
With reference to FIG. 1, in the configuration of the current state of the art, a link 1′ includes a fastening ring 30′ at one end and a yoke 20′ at the other end. It is composed of two sections: the ring is provided with a threaded rod 31′ co-operating with a tapered orifice 11′ in the yoke 20′. The length of the link 1′ is adjusted by rotating one part relative to the other and both parts are immobilised together by means of a nut 32′ locking a washer 33′ slid onto the threaded rod 31′. The nut 32′ is locked, for its own part, by a metal wire. The assembly and the adjustment of the link are not easy since one of the attachments must be released in order to proceed to the adjustment in length. The adjustment accuracy is determined; it is given by the variation in length generated by the rotation over half a turn. In this example, the adjustment is 0.45 mm by semi-turn.
This type of link exhibits the shortcoming in aeronautics that it must be made of a suitable material compatible with a threading. Steel is therefore used. However, the mass of this metal is high with respect to other metals used generally in this field, and especially it is corrosion sensitive. Besides, the link is composed of five different parts, which is a detrimental factor in terms of management and maintenance.